ee ALLEN, ‘ Aptosochromatism.’ 225 
wholly inadequate assumptions, namely: (1) the case of the 
Golden Plover, in which he says, “if a specimen be examined in 
spring, we find the white feathers on the breast in all stages of 
colour between white and black. Messrs. Allen and Stone would 
have us believe that these are all new feathers, which have grown 
of that colour, and which will always remain of that colour.” In 
summer Mr. Bonhote finds that the ‘‘ many birds in the full sum- 
mer dress ”’ that he has examined rarely have ‘“‘ more than one or 
two feathers in this half-and-half stage on any single individual.” 
The conclusion reached is that the Golden Plover assumes the 
breeding dress “by direct moult’’ on the back while it acquires 
‘its black breast by the white feathers turning black. ‘The new 
growing feathers on the breast,’ he says, “are wz¢e, not black 
or particoloured, and then change to the black summer dress.” 
I cannot say from personal observation what the European 
Golden Plover does, but the American Golden Plover and its 
near ally, the Black-breasted Plover, acquire the black breast 
feathers by a moult, as the examination of a large number of 
specimens has abundantly shown.! (2) As to the physiological 
process involved in this change of white feathers to black ones, 
Mr. Bonhote says: “I am not in a position to write about it at 
present, but should like to draw attention to a paper by M. V. 
Fatio, in which he shows that an oil is continually making its way 
into the feather from the body.” As ‘*most pigments are soluble 
in ether, alcohol, or chloroform,” they are thus proved ‘to be 
of an oily nature. Now, if it has been proved that oil can make 
its way up a feather, and, further, that all true pigments (black, 
red, and their combinations) are of an oily nature, it necessarily 
follows that pigment can make its way up also.’”’ Yet it is ad- 
mitted “ that this flow is not due to any active agent, but to osmo- 
sis, capillarity, or some similar action’?! We know the results of 
capillarity ; its action is evident as a mechanical process in a 
thousand ways. But what has this to do, we may ask, with the 
1 Since this article was sent to the printer we have received the manuscript 
of Dr. Dwight’s important paper, given later in this number of ‘The Auk,’ on 
the ‘Moult of the North American Shore Birds (Limicolez),’ to which 
the reader’s attention is especially called in reference to the Golden and 
Black-bellied Plovers. 
